A fuel cell generates power by an electrochemical reaction between hydrogen and oxygen, and water vapor is produced at the same time. Further, the hydrogen or air used by the fuel cell is humidified before it is supplied. Therefore, there is always water in the fuel cell power plant, and when the fuel cell power plant stops operating under low temperature conditions, this water freezes during the period when the fuel cell power plant is not operated, and may interfere with the restarting of the power plant when it next starts up.
JP10-223249A published by the Japanese Patent Office in 1988 proposes discharging condensed water in the fuel cell power plant after a certain time has elapsed from when the power plant stops operating, so as to avoid this water freezing in the fuel cell power plant.
Specifically, the water remaining in internal passages is discharged by opening drains provided at certain sites in the power plant. The reason why the drains are opened after a certain time from when the power plant stops operating is that a predetermined time is required for water vapor to condense due to the temperature drop after operation has stopped.